Arterial blood sampling practices in intensive care units in England and Wales.

A postal survey of arterial blood sampling practices in 280 intensive care units throughout England and Wales found that very few measures are taken to reduce diagnostic blood loss in adult intensive care patients from arterial sampling. The average volume of blood withdrawn to clear the arterial line before sampling is 3.2 ml; subsequently returned to the patient in only 18.4% of intensive care units. Specific measures to reduce the blood sample size by the routine use of paediatric sample tubes in adult patients occurs in only 9.3% of intensive care units. In paediatric units, the average volume withdrawn was 1.9 ml and this was routinely returned in 67% of units. Some aspects of arterial blood sampling practices identified in this survey may contribute to iatrogenic anaemia in intensive care patients.